The present invention relates to medical fluid injectors for injecting medical fluid into patients.
Injectors are devices that expel fluid, such as contrast media, from a syringe and through a tube into an animal. The injectors are provided with an injector unit, usually adjustably fixed to a stand or support, and have a drive ram that couples to the plunger of the syringe to drive it forward to expel fluid into the tube, or to drive the plunger rearward to draw fluid into the syringe to fill it. Usually the syringe is a disposable replacement type.
U.S. Pat. No. 5,300,031, which is assigned to the same assignee as this application, discloses a front-loading injector. This injector has a pressure jacket mounted to its front face for receiving a syringe. A syringe having an open back end is inserted into the pressure jacket and coupled to the pressure jacket by a rotating motion. This same rotating motion causes the plunger in the syringe to couple to the end of the ram. The pressure jacket supports the side walls of the syringe against injection pressure during operation of the injector. After an injection, a reverse rotating motion unlocks the syringe from the pressure jacket and releases the plunger from the ram, so the syringe can be removed and replaced.
An advantage of this front-loading structure, as compared to prior, breach-loading structures, is that the syringe may be disconnected and removed from the injector after an injection, while the ram is in its forwardmost position. Furthermore, while the ram remains in its forwardmost position, a new syringe may be inserted into the pressure jacket, over the ram, and locked to the pressure jacket and ram. Then, filling of the syringe for the new injection can immediately commence. When loading and unloading operations are performed with the ram in a forward position, the pressure jacket serves as a guide to prevent the ram from contacting the internal surfaces of the syringe, thus preserving sterility of the internal surfaces of the syringe. Accordingly, removal and replacement of a syringe can be accomplished without extraneous movement of the ram and without risks of loss of sterility.
A second front-loading injector structure is disclosed in U.S. Pat. No. 5,383,858. This front loading injector structure is similar in many respects to that disclosed in U.S. Pat. No. 5,300,031, with the main difference that the injector of U.S. Pat. No. 5,383,858 does not include a pressure jacket on the front surface thereof. Rather, the syringe is made of a hard plastic material which is deemed sufficiently self-supporting to withstand injection pressures. In the front-loading injector of U.S. Pat. No. 5,383,858, the syringe and injector, and the plunger and ram, are connected to each other by a single twisting motion, and disconnected from each other by a reverse twisting motion; thus, the connection and disconnection procedures are similar to that used by the injector of U.S. Pat. No. 5,300,031.
A disadvantage of the injector of U.S. Pat. No. 5,383,858, is that, while it is possible to remove the syringe of U.S. Pat. No. 5,383,858 from the injector, while the ram is in a forward position, and to insert a new syringe to the injector while the ram remains in this forward position, and even tempting to do so, this procedure for loading and unloading a syringe is not advisable. The injector of U.S. Pat. No. 5,383,858 lacks a pressure jacket or any other mechanism for preventing the internal surfaces of the syringe from contacting the end of the drive ram. Accordingly, it is likely that a user of the injector, attempting to remove and replace a syringe on this injector with the ram in its forward position, will accidentally contact the interior surface of the syringe with the end of the ram, contaminating the interior of the syringe and risking infection to the patient. Unfortunately, however, users of the injector of U.S. Pat. No. 5,383,858, particularly those users familiar with the injector shown in U.S. Pat. No. 5,300,031, are likely to be tempted to remove and replace syringes with the ram forward.
Thus, there is a need for an adapter for the injector of U.S. Pat. No. 5,383,858, which can be fitted to that injector to prevent the user of the injector from attempting to remove the syringe with the ram forward of its rearwardmost position.
In accordance with a first aspect of the present invention, an adapter is incorporated into the face plate of the injector of U.S. Pat. No. 5,383,858, to prevent the user of the injector from rotating the syringe when the ram of the injector is at other than its rearwardmost position. Specifically, the adapter includes a channel for receiving a rearward end of a syringe. This channel interacts with mounting structure on a rearward end of the syringe, so that the syringe may be inserted into and then rotated in the channel to lock the syringe to the adapter. The adapter further includes one or more locking pins, which in a locked position extend across the channel, to block the syringe from rotating in the channel and thereby prevent a syringe from being mounted to or dismounted from the adapter, and which in an unlocked position do not extend across the channel and do not block the syringe from rotating in the channel to mount or dismount to or from the adapter. A cam member incorporated in the adapter interacts with a drive ram of the injector to move the locking pins between the locked and unlocked positions, so that the locking pins move into their locked position whenever the ram is forward of a rearwardmost position.
In specific embodiments, the cam member is a collar, which fits over the tip of the ram. The locking pins are integral with the collar, and extend from the collar through the adapter and, in their locked position extend into the channel on the front surface of the adapter. Resilient elements (e.g., springs) mounted in the adapter generate a force tending to push the collar forward to the locked position. The collar interacts with the ram such that when the ram is withdrawn from the syringe, the ram engages the collar and withdraws the collar and the locking pins integral therewith rearwardly into the injector. This rearward motion draws the locking pins out of the channel on the front surface of the injector, permitting a syringe to be mounted to the injector. A ram tip extender is attached to the ram disclosed in U.S. Pat. No. 5,383,858, which extender includes cam surfaces for engaging the collar to draw the collar backward.
In accordance with another aspect of the present invention, a novel ram tip is used in connection with a front loading injector. This ram tip includes movable member having a connector for engaging a connecting structure on a rearward face of a plunger, and a cam surface for interacting with the injector to move the movable member when the ram tip is in a rearward position. The interaction between the cam surface and the injector causes the connector of the movable member to move between an engaging position in which the connector engages with the connecting structure of the syringe, and a disengaging position in which the connector does not engage the connecting structure of the syringe.
In specific embodiments, the ram tip comprises a second movable member, including a second connector and a second cam surface, where the interaction of the second cam surface with the injector causes the second connector of the second movable member to move between an engaging position in which the second connector engages with the connecting structure of the syringe, and a disengaging position in which the second connector does not engage the connecting structure of the syringe.
The movable members move by rotating between the engaging and disengaging positions. The connectors on the movable members are hooks, which project radially outward when the movable members are rotated into their engaging positions, and are positioned at a radially inward position when the movable members are rotated to their disengaging positions. The cam surfaces are ramp members which contact mating ramp members on a front surface of the injector, causing the movable members to rotate inwardly toward their disengaging positions. A resilient element produces a force tending to position the movable members in their engaging positions absent a counteracting force applied to the cam surfaces.
The above and other objects and advantages of the present invention shall be made apparent from the accompanying drawings and the description thereof.